BRAINERD, Minn. — State wildlife officials say adult zebra mussels have been found in Cross Lake and Lower Hay Lake — two of the 14 lakes in the Whitefish chain in central Minnesota.

The state Department of Natural Resources is reminding boaters and property owners to take precautions to avoid spreading the invasive species, the Brainerd Dispatch reported (http://bit.ly/15E8e3O ).

Zebra mussels are an invasive mollusk that arrived in the Great Lakes in the 1980s, apparently by hitching a ride on ocean-going ships.

DNR spokesman Mike Duval said the discovery of zebra mussels in the two lakes doesn't mean they're in all the lakes in the chain. That means proper precautions could still make a difference.

The agency has put up signs at public and private access points on the Whitefish chain to raise awareness. Duval directed boaters and property owners to the DNR website for ways to help curb aquatic invasive species.

Dave Fischer, president of the Whitefish Area Property Owners Association, said he was disappointed at the discovery of the zebra mussels. He said his group would continue its strategy of educating people and inspecting watercraft. He said his group has paid and unpaid inspectors who check boats at the access points.

"We need all Minnesotans to recognize that this is an issue which increasingly impacts them, both financially, and ecologically, whether or not they spend time on our lakes and rivers," he said.

The Whitefish chain has 14 lakes and 199 miles of shoreline, and seven access points.

Zebra mussels attach themselves to hard surfaces such as boats, boat lifts and native mussels. Duval said researchers were still learning about the effects they can have on a habitat.

Other Brainerd-area waters infested with zebra mussels include Ossawinnamakee Lake, Rice Lake, Gull Lake and Pelican Lake, Duval said. They were also discovered in Lake Winnibigoshish this year and in Round Lake last year.